Curable fluoroelastomer composition
Fluoroelastomer compositions comprising fluoroelastomers having copolymerized units of a nitrile-containing cure site monomer are cured with certain hydrazone or oxime curatives.
1. A curable composition comprising:
A) a fluoroelastomer comprising copolymerized units of vinylidene fluoride or tetrafluoroethylene; and copolymerized units of a nitrile group-containing cure site monomer; and
B) a hydrazone or oxime of the general formula R 1 (C═NY) n R 2 wherein n=1 or 2, Y=OH, or NH 2 , R 1 is aryl, alkyl, perfluoroalkyl, benzyl or heterocyclic and R 2 is aryl or heterocyclic.
2. The curable composition of claim 1 , wherein n is 1; R 1 is aryl, R 2 is aryl and Y is NH 2 .
3. The curable composition of claim 1 , wherein n is 1; R 1 is aryl, R 2 is aryl and Y is OH.
4. The curable composition of claim 1 wherein n is 1; R 1 is aryl or heterocyclic, R 2 is aryl and Y is NH 2 .
5. The curable composition of claim 1 wherein n=2 and the hydrazone is C 6 H 5 (C═NNH 2 ) 2 C 6 H 5 .
6. The curable composition of claim 1 , wherein R 1 and R 2 are aryl and fused together to form a fluoroenyl, and Y is NH 2 .
7. The curable composition of claim 1 , wherein an appropriate level of hydrazone or oxime is selected by the time necessary to develop maximum moving die rheometer (MDR) torque and minimum Mooney scorch of the curable composition.
8. The curable composition of claim 7 , wherein a carbonyl group is not adjacent to the hydrazone or oxime.
9. A cured article made from the composition of claim 1 .
10. A cured article made from the composition of claim 8 .
11. A curable composition consisting of:
A) a fluoroelastomer comprising
copolymerized units of vinylidene fluoride or tetrafluoroethylene; and
copolymerized units of a nitrile group-containing cure site monomer; and
B) a hydrazone of the general formula R 1 (C═NNH 2 ) n R 2 wherein n=1 or 2, and R 1 is aryl, alkyl, perfluoroalkyl, or heterocyclic and R 2 is aryl or heterocyclic.
12. A cured article made from the composition of claim 11 having a volume swell, measured according to ASTM D1414, after exposure to 225° C. water for at least 168 hours of less than 1% and a compression set, 300° C., 70 hours, 15% compression, measured according to ASTM D395, of less than 70%.